Cryogenic insulation system



sept. 12, 1967 .C. D. FORMAN ETAL CRYOGENIC INSULATION SYSTEM Filed Non 16, 1964 FIG.v 1

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DETECTOR INVENTORS CHARLES D. FORMAN wHELAN, cHAsAN, LITToN, MARX a wmGHT ATTORNEYS AUGUSTUS B. SMALLl United States Patent O 3,341,049 CRYOGENIC INSULATHON SYSTEM Charles D. Forman, Elizabeth, and Augustus B. Small,

Westfield, NJ., assignors to Esso Research and Engineering Company, a corporation of Delaware Filed Nov. 16, 1964, Ser. No. 411,397 8 Claims. (Cl. 220-9) ABSTRACT OF 'IHE DISCLQSURE An insulated container having two liquid-tight barriers which are provided by cladding a closed container, typically in the form of a cargo hold, with prefabricated, dimensionally stable insulating panels which constitute a continuous secondary barrier, to which barrier relatively flexibly interconnected cargo-resistant panels are loosely and independently secured to define a superimposed, continuous primary barrier.

The present invention relates to integral insulation systems, and more p-articularly, to a new and improved insulated container structure for the storage and marine transportation of liquefied natural gas cargoes at atmospheric pressures under which conditions the liquid cargoes are at cryogenic temperatures -and require structures of sufficient strength and displacement compensating characteristics to withstand the unusually large temperature gradients which exist from the outer, relatively warm side of the container to the inner, supercooled cargo side.

In accordance with the principles of the present invention, an insulated container having two liquid-tight barriers is provided by cladding a closed container, typically in the form of a cargo hold, with prefabricated, dimensionally stable insulating panels which constitute a continuous secondary barrier, to which barrier relatively dimensionally unstable, flexibly interconnected cargo-resistant panels are loosely and independently secured to define a superimposed, continuous primary barrier. The insulating panels employed are generally similar in construction to those disclosed in the copending Harold Pratt et al. Iapplication Ser. No. 394,287, for Insulation System, filed Sept. 3, 1964, and, in accordance with the present invention, the independently movable primary barrier is formed from a plurality of triplex panels which are of a sandwiched construction, the outer layers of which are thin sheets and the intermediate layer of which is a thin honeycomb core. The specific shape of the triplex panel itself is defined by a frame to which the outer sandwiching sheets are suitably adhered.

As an important specific aspect of the invention, the

triplex, primary barrier panels are relatively loosely mounted to the secondary insulating barrier to accommodate free and independent displacement thereof with respect to the insulating panels from which they are supported. This independent displacement, as will be understood, accommodates the induced changes in dimension of the primary panels, which are experienced when the triplex panels are subjected to cryogenic temperatures, without unduly stressing the supporting insulating panels. Continuity of the primary barrier is provided and maintained by flexible bellows-like elements which extend between adjacent primary panels in the completed insulated structure to accommodate relative mutual displacement of the individual triplex panels, themselves.

A high degree of fail safety is inherent in the new system, since the novel iiexible and independent mounting of the primary barrier to the secondary barrier insures that a failure in one will not cause a failure in the other. Furthermore, the new insulating system is made safer yet by the incorporation therein of a monitoring system to detect any leakage which may develop through a failure in the primary barrier. To that end and in accordance with another specific aspect of th-e invention, the frame and intermediate honeycomb structure of the triplex panels are provided with orifices to define a cargo passage for any leakage that might penetrate the primary barrier through cracks therein. The passages of each of the panels are effectively interconnected to form a network which is in constant communication with a cargo monitoring device. Thus, leakage through the primary barrier will be readily and immediately detected through a system employing the primary barrier panels, themselves, as conduits.

For a more complete understanding of the present invention and the attendant advantages, reference should be made to the following detail-ed description taken in conjunction with the accompanying drawings in which:

FIG. 1 is a cross-sectional view of an insulated container, embodying the concepts of the present invention in ,a cargo hold of a ship; and

FIG. 2 is an enlarged fragmentary cross-sectional View, taken along line 2-2 of FIG. l, showing details of construction of the new and improved integral insulation system for the transportation of cargoes at cryogenic temperatures at atmospheric pressures. 4

Referring to FIG. l, the integral insulation system of the present invention, a system in which the primary barrier is directly supported by the secondary insulating barrier, is shown in a preferred embodiment in the cargo hold of a double-hulled tanker 10. The insulation system includes a secondary liquid-tight barrier in the form of a continuous insulating layer 11 supported in an endto-end, side-by-side relation by the inner hull structure 12 of the ship and a primary liquid-tight barrier 13 superimposed upon the secondary barrier 11 and directly, but independently, supported thereby.

Specifically :and as shown in FIG. 2, the continuous, eectively dimensionally stable, secondary barrier 11 is established by securing stepped insulating panels 14, through integral flanges 16 extending peripherally out wardly from base portions thereof, to the inner hull plate 12 by means of a nut 15 and a Nelson stud 15. Advantageously, the insulating panels 14 are generally similar to those dimensionally stable panels disclosed in more det-ail in the above-identified copending application of Harold Pratt et al. More specifically, the panels 14 are approximately five feet by twenty-five feet in size, are generally symmetrical in shape (FIG. 2 showing opposite sides of two panels), and include glass fiber reinforced polyester shells 17 filled with polyurethane foam 18. Each gap 19 formed between opposing faces 20 of adjacent insulating panels 14 is closed by a matingly stepped plug piece 21, constructed similarly to the insulating panels 14 of a glass liber reinforced polyester shell filled with polyurethane foam and being correspondingly effectively dimensionally stable.

The secondary barrier 11 defined by the end-to-end and side-by-side arr-ay of insulating panels `and plug pieces, is made continuous and liquid tight by the adherence of the plug pieces 21 to the opposing stepped faces 20 of adjacent insulating panels by means of a suitable adhesive sealant 22. As set forth in more detail in the beforem-entioned Pratt et al. application, the above-described insulating secondary barrier 11 is effectively dimensionally stable and will not undergo deleterious contraction when subjected to the extreme temperatures (e.g., -258 F. for liquefied methane) encountered in the cryogenic environments of liquefied natural gases.

In accordance with the principles of the present invention, the cargo-resistant, primary barrier is formed by a plurality of triplex panels 24, the generally rectangular supercooling temperatures of the cargo,

shape of each of which is defined by a peripheral aluminum frarne 25 advantageously fabricated from an extruded C-shaped aluminum channel. As shown in FIG. 2, the triplex panels 24 include inner and outer metal foil or plastic layers 26, 27, respectively, which a-re welded or otherwise suitably united with the frame members 25 and which are maintained in a predetermined spaced relation of approximately one-half inch, by an intermediate, cargo-resistant honeycomb structure 2S. The honeycomb structure 2S is made from glass fiber reinforced |polyester, phenolic-impregnated paper, aluminum, or like material, which contributes to the strength of the triplex panel 24 and to its insulating properties by providing dead air space 29 therein. Desirably, the inner and outer layers 26, 27 and the frame 25 have similar thermal coefficients of expansion. Accordingly, aluminum foil, typically of about 0.025 inch thickness, is a most suitable material for the primary barrier layers 26, 27 when an aluminum frame is employed.

In accordance with an important aspect of the invention, the triplex primary barrier panels 24 are independently and yieldably supported from the secondary insulating barrier. To that end and in accordance with the present invention each of the plug pieces 21 of the dimensionally stable insulating barrier 11, defines an inverted T-shaped open keyway 23. By lightly clamping the lower flanges 30 of the triplex panel frame 25 between a longitudinal aluminum or stainless steel mounting plate 31, freely supported in the keyway 23, and the face 11 of the secondary barrier, the primary barrier panels 24 may be supported from the secondary barrier with sufficient freedom of movement to be independently displaceable relative thereto.

More specifically, a lock nut 32 is lightly tightened down upon a stud 33, which is projected inward from the mounting plate 31 and through an opening 34 in the face of secondary barrier 11', by means of a clamping plate 35 which extends substantially beyond the edges of the gap 36 formed between the faces of the outer flanges 30 of opposing adjacent frame members 25. As will be understood, the gap 36 will be increased when the adjacent triplex panels contract from exposure to the cryogenic cargo. Accordingly, the width of the clamping plate is predetermined to bridge the gap and provide loose clamping under all temperature conditions and ensuing gap widths. Advantageously, the triplex primary barrier panels are free of the secondary barrier panels, except at the peripheral points of attachment with the studs 3.3-,

The continuity of the primary barrier is established, in accordance with the present invention, by connecting the opposing adjacent inner flanges 37 of the adjacent frame members 25 with a flexible bellows 38 constructed from aluminum foil or sheet similar to that of the inner and outer layers 26, 27 of the triplex panel. As shown, the bellows 38 is bonded to adjacent triplex panels and is additionally secured in grooves 25' formed therein.

As an important aspect of the invention, the honeycomb structure 28 is provided with a series of perforations or orifices 41 in communication with ports 42 formed in opposite web portions 46 of the frame 25'. As will be appreciated, each of the triplex panels 24 thus provides a continuous passage therethrough, which passage directly communicates with the passages formed in the adjacent triplex panel to establish, in accordance with the inventive principles, a leakage detection network. A gas detector 43 is directly linked with the established detection network, through piping 45 and an opening 44 formed in the aluminum foil layer 26 of the primary barrier, for the immediate sensing of cargo in the detection network.

In accordance with the principles of the invention, shrinkage of the continuous primary barrier 13 will be accommodated by the bellows connections of the triplex panels and their loose or flexible mountings to the secondary barrier. Specifically, upon being subjected to the each of the triplex panels 24 is free to contract, independently of the dimensionally stable secondary barrier, and in doing so to increase the gap 36 between the adjacent frames 25. As should be understood, the bellows structure 38 iaintains the continuity of the primary barrier, since it is sufficiently oversized to maintain the bridge between adjacent panels when the panels increase their mutual separation through contraction and the bellows material, itself, contracts due to the cryogenic temperatures. As will be further understood, the clamping member 35, which is of sufficient length to maintain a loose clamping contact with the adjacent frame flanges 30, maintains the independent support of the triplex panels from the sec- Y ondary insulating structure while accommodating their displacement relative thereto.

The novel independent mounting of the primary barrier to the secondary barrier provides a great degree of fail safety, since a failure of the secondary barrier will not cause a corresponding failure in the primary barrier layer. Correspondingly, a failure in the primary layer will not cause a failure in the secondary barrier layer. This high degree of fail safety is further enhanced, as may readily be appreciated, by the creation of an integral leakage detection network in the primary barrier panels themselves to provide immediate warning of any cargo leakage through the layer of the primary barrier.

Furthermore, the new insulation system may be constructed with maximum efficiency. Thus, as the secondary insulating layer is progressively built up, the primary triplex panels may be superimposed thereover and ilexibly mounted thereto with minimum effort and great expediency. The closed insulated container thus formed in accordance with the principles of the present invention is highly reliable and extremely fail safe.

It should be understood that the specific structure herein illustrated and described is intended to be representative only, as certain changes may be made therein without departing from the clear teachings of the disclosure. Accordingly, reference should be made to theV following appended claims in determining the yfull scope of the invention.

What is claimed is:

1. An insulated container structure for materials maintained at cryogenic temperatures and atmospheric pressures comprising:

(a) a rigid outer supporting structure,

(b) a plurality of effectively dimensionally stable insulating panels arrayed in a general end-to-end and side-by-side relation,

(c) means maintaining said panels in said array and against said outer rigid constructure, stepped edge plug means interposed between said panels,

(d) adhesive sealing means joining said stepped edge plug means to adjacent ones of said insulating panels in -a manner whereby said panels cooperatively define a continuous liquid-tight secondary barrier,

(e) a plurality of triplex primary barrier panels having peripheral frame members supporting spaced layers of cargo-resistant sheet material sandwichng honeycomb structures therebetween,

(f) said frame members having inner and outer anges,

(g) flexible bellows-like elements interconnecting the inner flanges of adjacent triplex panels,

(h) lmounting means slidably engaging said plug means to hold said triplex panels against said insulating panels while accommodating relative movement therebetween,

(i) whereby said triplex panels define a continuous primary barrier which is freely movable relative to and independently of said secondary barrier.

2. An insulated container structure in accordance with claim 1, in which v- (a) said frame members define ports therein at opposite sides thereof,

(b) said honeycomb structures define passages therethrough and in communication with said ports,

(c) said passages of said triplex panels cooperating to define a leakage detection network, and

(d) a -gas sensing means is associated with said network and adapted to detect the presence of gas therein.

3. An insulated container in accordance with claim 1,

in which (a) said insulating panels are comprised of glass fiber reinforced polyester lshells filled with foamed polyurethane,

(b) said cargo resistant sheet material and said peripheral frame members are aluminum.

4. An insulated container in accordance with claim 1,

in which (a) said plug means including a keyway immediately below the face thereof,

(b) said mounting means includes a mounting plate supported in said keyway,

(c) a stud means is associated with said mounting plate and extends inwardly through the face of said plug means and between adjacent frame members,

(d) a lock nut means is associated with said stud means,

(e) said mounting means further including a clamping plate in contact with the outer anges of said adjacent frame members,

(f) said clamping plate with a light clamping force urges said frame members against the face of said plug means and secondary barrier in a manner whereby said frame members are freely and independently movable relative to said secondary barrier.

5. An insulated wall for a cryogenic insulation system including (a) a rigid outer supporting structure,

(b) a plurality of effectively dimensionally stable insulating panels,

(c) means mounting said insulating panels to said supporting structure, plug means interposed between said panels, adhesive sealing means joining said plug means to adjacent ones of said panels, whereby said insulating panels define a cryogenic liquid-tight secondary barrier,

(d) a plurality of triplex panels including spaced sheet members supported by peripheral frame elements and sandwiching honeyc-omb core structures therebetween,

(e) said frame elements including inner and outer peripheral flanges, (f) mounting means slidably engaging said plug means to hold said triplex panels to said plug means and 5 secondary barrier to accommodate relative movement therebetween, and (g) flexible bellows means interconnecting said inner flanges whereby said interconnected triplex panels define a cryogenic liquid-tight primary barrier super- 10 imposed on said secondary barrier and independently displaceable relative thereto. 6. An insulated Wall in accordance with claim 5, in which (a) said sheet members and frame elements of said triplex panels are aluminum, and

(b) said bellows-like means are aluminum. 7. An insulated wall in accordance with claim 5, in which (a) said honeycomb core structures dene a plurality yof orifices therein,

(b) said frame elements define openings therein cooperating with said orifices to define a continuous gas passage through said triplex panels.

8. An insulated wall structure in accordance with claim 7, in which (a) a gas detecting means is operatively associated with said passage and is adapted to detect leakage of gas through said sheet members.

References Cited UNITED STATES PATENTS 2,708,774 5/ 1955 Seelen 22o- 2.1 2,728,702 12/1955 Simon et al 220-9 2,772,860 12/ 1956 Nelson 220-63 2,983,401 5/ 1961 Murphy 220-10 3,020,669 4/ 1962 Dosker 220-10 3,031,856 5/ 1962 Wiedemann et al 220-9 3,150,793 9/ 1964 Messer 220-9 3,158,383 11/1964 Anderson et al 220-9 3,158,459 11/1964 Guilhem 220-15 3,189,211 6/ 1965 Podlaseck 220-9 3,273,740 9/ 1966 Herrenschmidt 220--9 THERON E. CONDON, Primary Examiner.

JAMES R. GARRETT, Examiner. 

1. AN INSULATED CONTAINER STRUCTURE FOR MATERIALS MAINTAINED AT CRYOGENIC TEMPERATURES AND ATMOSPHERIC PRESSURES COMPRISING: (A) A RIGID OUTER SUPPORTING STRUCTURE, (B) A PLURALITY OF EFFECTIVELY DIMENSIONALLY STABLE INSULATING PANELS ARRAYED IN A GENERAL END-TO-END AND SIDE-BY-SIDE RELATION, (C) MEANS MAINTAINING SAID PANELS IN SAID ARRAY AND AGAINST SAID OUTER RIGID CONSTRUCTURED, STEPPED EDGE PLUG MEANS INTERPOSED BETWEEN SAID PANELS, (D) ADHESIVE SEALING MEANS JOINING SAID STEPPED EDGE PLUG MEANS TO ADJACENT ONES OF SAID INSULATING PANELS IN A MANNER WHEREBY SAID PANELS COOPERATIVELY DEFINE A CONTINUOUS LIQUID-TIGHT SECONDARY BARRIER, (E) A PLURALITY OF TRIPLEX PRIMARY BARRIER PANELS HAVING PERIPHERAL FRAME MEMBERS SUPPORTING SPACED LAYERS OF CARGO-RESISTANT SHEET MATERIAL SANDWICHING HONEYCOMB STRUCTURES THEREBETWEEN, (F) SAID FRAME MEMBERS HAVING INNER AND OUTER-FLANGES, (G) FLEXIBLE BELLOWS-LIKE ELEMENTS INTERCONNECTING THE INNER FLANGES OF ADJACENT TRIPLEX PANELS, (H) MOUNTING MEANS SLIDABLY ENGAGING SAID PLUG MEANS TO HOLD SAID TRIPLEX PANELS AGAINST SAID INSULATING PANELS WHILE ACCOMMODATING RELATIVE MOVEMENT THEREBETWEEN, (I) WHEREBY SAID TRIPLEX PANELS DEFINE A CONTINOUS PRIMARY BARRIER WHICH IS FREELY MOVABLE RELATIVE TO AND INDEPENDENTLY OF SAID SECOND BARRIER. 